I guess the reason it jars us here is because most people post properly.
Except the gmail lusers who haven't figured out how to turn off multipart html crap.
+1
Unfair: the 'text' formatting mode from GMail is very standard compliant, trimming the lines etc.
Maybe one should just more explicitly tell new users to enable it when posting to mailing-lists. This is even easier to activate (this hyperlink right here above the text area) than in any mail client I have ever seen (except those which do only text, of course...)